Circuit interrupter



Sept. 20, 1932. MCGEE ET AL 1,878,959

CIRCUIT INTERRUPTER Filed Sept. 27. 1928 INVENTORS. JO/m [IN-Gee 8 Benjamin PEa/(er.

ATTORNEY Patented Sept. 20, 1932 UNITED STATES PATENT OFFICE JOHN E. 'MCGEE AND BENJ'AKIN P. BAKER, OI WILKINSBUBG, PENNSYLVANIA, AS- SIGNOBS '10 WESTINGHOUSE ELECTRIG AND MANUFACTURING OOMPANY, A COB- PORATION 0] PENNSYLVANIA CIRCUIT INTERRUPTEB Application fled September Our invention relates to circuit interrupters and more particularly to arc-extinguishing devices therefor.

One object of our invention is to provide an arc chute for a circuit interrupter that shall have a consumable material associated with the inner walls thereof adjacent to the arc path to prevent the condensation of the metallic vapors from forming a conducting deposit the full length of the walls of the arc chute.

Another object of our invention is to provide an arc chute that shall have a material that is not affected by the heat of the arc, inlaid in the portion of the walls opposite the point of reatest arc intensity.

A furt er object of our invention is to provide an arc chute with alternate sections of consumable and refractory material forming side walls that shall have the alternate sections so placed that the consumable material will at all times provide a clean insulating surface while the refractory material resists most of the burning and condenses most of the metallic vapor.

Heretofore arc chutes of refractory material for circuit interrupters were limited in their application due to the deposit of metal on the walls thereof adjacent to the arc path when employed on high voltage circuits. If a material were employed that would be consumed by the arc in order to carry away this depwit, the insulating qualities of the air or other gas, within the chute and immediately below it would be so reduced as to further limit is application.

It is the further object of our invention to combine these two types of materials in order to rovide boththe insulating qualities required for an arc chute and also to provide a means for preventing excessive deterioration and liberation of unburned combustible material from the walls adjacent the contact members.

These, and other objects that will be made apparent throughout the further description of our invention, are attained by the arc, chutes hereinafter described and illustrated in the drawing, wherein:

Figure-1 is a view in sectional elevation i1 27, 1928. Serial No. 808,719.

lustrating our improved switch mechanism; Fig. 2 is a sectional view of the structure in Figure 1;

Fig. 3 is a view of a schematic arrangement of a particular embodiment of our imfrom pieces of desired dimensions or moldedfrom a material that has the desired insulating properties.

The are chute 1 encloses the moving contact 6 and the stationary contact 7 that are positioned midway between or at one end of the side walls 2 and 3. The contact member 7 is attached to a fixed arm 8 by a bolt 9 and Washers 11. The moving contact 6 is carried by a movable member 12 and is attached thereto by bolt 13 and washer 14. The members 12 and 8, together with the contacts 6 and 7, form the arc drawing members of a circuit interrupter not otherwise shown.

Referring to Figs. 1 and 2, the side walls 2 and 3 have openin 15 and 16 formed therein in which the projections 17 and 18 of refractory members 19 and 21 are heldin fixed position. The members 19 and 21 are of considerable thickness and extend from the inner surface of the side walls 2 and 3 to within close proximit of the sides of the contact members 6 and The side walls 2 and 3 of an arc chute disclosed in the copending application of A. L. Van Emden, Serial No. 264,995, filed March 27 1928, and assigned to the assignee of the present application, are composed of fibre or some other combustible substance upon which the metallic arc vapors will condense. The surface of the walls are consumed by the arc and, the metallic deposit is freed and ejected fromthe arc chamber along with the consumed material and a clean surface free from the metallic condensation will be maintained in the vicinity of the fuse terminals.

In applying the consumable material to circuit interrupters in which the main contact members are'located in close roximity a re-initiation of the arc may take place under certain conditions. Investigation shows that the combustible material, after becoming detached from the side walls, is probably incompletely burned and, when it is carried into a region in which the atmosphere contains a large percentage of free oxygen, complete combustion thereof takes place. Such combustion tends to ionize the air between points of different potential, and cause an electrical discharge to follow.

In order to obviate this difficulty, in one form of our invention as shown in Figs. 3 and 4, we mount upon the surface of the arc chute walls, spaced sectional plates 19 and 21 made of an insulating material which does not carbonize when subjected to the high temperatures of the arc. The plates are spaced apart for the purpose of insulating them from one another and to provide a deep crevice between them for preventing the metal vapors of the arc gas from reaching the surface of the fibre wall between the plates, the metal being condensed upon the plates before it reaches the wall. In this manner, the arc chute walls in the vicinity of the contacts are provided with relatively small insulated sections upon which metal may be deposited without forming an extensive continuous conducting surface and the release of combustible articles in the vicinity of the contacts is ellminated.

Another form of arc-chute, that is within the purview of the present invention and that obviates the above noted difiiculty, is that in which the members 19 and 21 are made of materials such as soap-stone, chalk, plaster of Paris and the like. These materials may be consumed in a greater or less degree, by the action of the arc, but they do not char and produce glowing particles. The material is slowly eroded by the action of the arc and the disintergration of the surface prevents the objectionable deposit of metal from forming on the walls of the arc-chute. The metal is carried out of the arc chute by the eroded material, which does not burn and liberate ionizing gases.

It has been found that most of the burning takes place directly adjacent to the contacts just after they separate and that substantially all of the metal vapors are liberated during the initial formation of the arc. We take advantage of this localized burning and vaporization in the structure shown in Figs. 1 and 2 and provide the single members 19 and 21 that are made of refractory material and extends some distance from the arcchute walls directly adjacent to that part of the arc path where the arc is initially formed. Metal volatilizing from the electrodes 6 and 7 condenses on the surface of the extended members immediately after it is vaporized and very little, if any, deposit is formed on the side walls 2 and 3. It is to be understood that the refractory material may be erodable in order that the condensing metal particles may be carried away with the eroded material in the manner described.

While we have described and illustrated but two embodiments of our invention, it will be apparent to those skilled in the art that various modifications, substitutions, changes, omissions and additions may be made in the apparatus herein described and illustrated without departing from the spirit and scope of our invention as set forth in the appended claims.

We claim as our invention:

1. The combination with a circuit interrupter having separable arcing contact members and an arc chute associated with said members having the walls thereof made of a consumable but relatively highly refractory material that is disintegrated slowly at its surface by the arc incident to separation of the contacts whereby metal vapors condensing on the surface are carried away by the particles released by distintegration, of a plate of insulating material disposed flat-wise between the contact members and the said walls having higher refractory characteristics than the walls for protecting the walls in the immediate vicinity of the are from the intense heat thereof and for condensing thereon the metal vapor in the arc.

2. The combination with a circuit interrupter having separable arcing contact members and an arc chute associated with said members having the walls thereof made of a consumable but relatively highly refractory material that is disintegrated slowly at its surface by the arc incident to separation of the contacts whereby metal vapors condensing on the surface are carried away by the particles released by disintegration, of a plurality of spaced insulating plates having higher refractory characteristics than the said walls and disposed flat-wise between the contact members and the said walls and in spaced relation to constitute interrupted surfaces for protecting the walls in the immediate vicinity of the are from the intense heat thereof and for condensing thereon the metal vapors in the arc.

3. The combination with a circuit interrupter having separable arcing contact members and an arc chute associated with said members having the walls thereof made of a consumable but relatively highly refractory material that is disintegrated slowly at its surface by the arc incident to separation of the contacts whereby metal vapors condensing on the surface are carried away by the particles released by disintegration, of a plate of insulating material disposed flat-wise beside the contact members and along the said walls and in the immediate vicinity of said contact members, said insulating material having higher refractory characteristics than the walls for eliminating excessive burning of the walls in the immediate vicinity of the are by the intense heat thereof. and for condensin thereon the metal vapor in the arc.

4. The combination with a circuit interrupter having separable arcing contact members and an arc chute associated with said members having walls of a consumable but relatively highly refractory material that is disintegrated slowly at its surface by the arc incident to separation of the contacts of a plate of insulating material having higher refractory characteristics than said walls disposed flat-Wise beside and in the immediate vicinity of the contact members for a portion only of the wall bounding the path of movement of the contact members whereby the surface of said are chute between the contact members when separated is partly of consumable material and part1 of highly refractory material with the highly refractory material positioned where the heat of the arc is of greater intensity.

In testimony whereof, we have hereunto subscribed our names this 15th day of September, 1928.

JOHN E. MOGEE. BENJALHN P. BAKER. 

